Z-Push seems not to connect to Kopano

I am trying to run Kopano and Z-Push on ArchLinux. So far everything works except for Z-Push. I have set Z-Push up according to some tutorials I have found on the internet, which basically comes down to changing the apache config for the php parameters needed as well as the Alias for ActiveSync and specifying the backend in z-push’s own config.

The issue is: when I check my setup by going to <serverURL>/Microsoft-Server-ActiveSync a login is shown but no matter what credentials I enter, the prompt just keeps reappearing. Credentials are obviously verified by using the Kopano WebApp but it also does not work with my iPhone, The logs show only very little information, even though I have set them to the most verbose settings.

I would have referred you to the z-push wiki, but confluence seems down at the moment (but it is https://wiki.z-hub.io/display/ZP/Installation for future reference). There you would also have found general install instructions.